Coated abrasive



Patented Dec. 15, 1942 arms? OFFI Q con-rap massive I Everett G. um, Troy, N. Y., assignor to Behr- Manning Corporation, Troy, N. Y., a corporation of Massachusetts No Drawing. Application July 17, 1936, Serial No. 91,177

1 Claims. (01. 51-295) This invention relates to the manufacture of coated abrasives, particularly coated abrasives that may be used either in the dry state or wet, but has more particular reference to coated abrasive papers that are to be used wet, usually after soaking in water to increase the flexibility of the product.

One object of the invention is to provide abrasive paper particularly adapted for use where water or water containing some wetting or lubricating agent is used on the work during the abrading operation. Another object of the invention is to produce a product of superior wet strength which will be resistant to disintegration during the abrading operation. Another object of the invention is to achieve superior wet strength combined with ready soaking or penetration of the backing by water to produce a softer product than would otherwise be the case. Another object of the invention is to provide a flexible product for the use indicated. Other objects will be in part obvious or in part pointed out hereinafter.

The invention accordingly consists in the features of construction, combinations of elements, arrangements of parts, and in the several steps and relation and order of each of said steps to one or more of the others thereof, all as will be illustratively described herein, and the, scope of the application of which will be indicated in the following claims.

I have found that the correct preparation of the base paper stock is important and as an illustration of my process, details instructions will be given for the manufacture of 40-1b. paper. The paper stock used may be rope, jute, chemical wood pulp or purified wood pulp, cotton, or various combinationsof these fibers. ,By way of illustration a suitable furnish may consist of 60% rope-fibers, suitably cooked as is known in the art, and 40% of a good grade of kraft pulp. The furnish is introduced into a beating engine and the paper stock is beaten to the required degree. By variations in the beating practice the penetration of the oil, varnish or other binder beaten to about a Schopper-Ri egler test of 30 degrees will be satisfactory. After the paper pulp has been sufliciently beaten, it is run through a Jordan to a Fourdinier paper machine and the sheet is formed in the usual way. The paper may also be 'dried in the regular way and taken down in the form of a large roll. It may then be treated on tub sizing equipment or other paper treating equipment with a 1% solution of viscose as cellulose which has been pretreated with sufilcient boric acid to practically neutralize the alkalinity of the viscose solution. Ammonium carbonate may then be added in suflicient quan= tities such that the liberation of carbon dioxide on the driers may tend to complete the regeneration of the cellulose, such completion of regeneration being subject to control through the amount of ammonium carbonate added.

In lieu of the foregoing treatment, viscose may be added in the beater but I have found that better results are usually obtained by adding the viscose to'the paper after the paper web is formed.

'In case the viscose is added in the beater, the

fiber furnish may be beaten to a higher degree,

if desired, to produce still greater resistance to oil penetration.

Instead of adding the viscose as a separate op eration after the paper has been taken down, it

may be added after the paper has had only a part of the water removed or during its passage through the drying cans, by the customary arrangements for tub sizing on a paper making machine.

The viscose used to impart wet strength to the sheet is decomposed after incorporation in the sheet to produce what is known as regenerated cellulose. By the term regenerated cellulose I mean the decomposition product of viscose or equivalent materials and a typical process of re generation is described in this specification. Even though no deliberate regenerating process is used, the viscose will eventually, decompose to yield regenerated cellulose and give the effect of a wet strength treatment.

Paper so treated is given a pre-treatment or I petroleum solvent such as Varnolene.

' oil and this will usually be desirable.

.- the varnish making process.

found advisable to thin this material with a For many purposes, a solution thinned to 78% heavy blown China-wood oil may be found suitable. A suitable temperature of application is 125 F. and a suitable coating arrangement for applying this solution is a set of calender rolls, one of which is made of rubber and one of which is made of .steel, as is well known in the art. For a back treatment of backsize, I may use a solution containing 60% of the same heavy blown China wood oil. A suitable temperature for the application of this coat is 110 F. and calender rolls similar to those used for applying a size to the coat side will be found satisfactory.

In lieu of China-wood oil on the coat side, I may use-varnishes made of China-wood oil and a small percentage of oil soluble Bakelite resins or other resinous materials. Asmall percentage of oil soluble phenolic resins often serves to decrease the penetration of the base paper by the For the backsize, in lieu of China-wood oil I may use an emulsion of a solution of fish glue in a thinner China-wood oil but in this case the temperature for applying the backsize should preferably be about 100 F. or lower. Many variations in the backsize and presize (used on the coat side) may be made.

Sometimes it may be found advantageous to omit the coat of oil or other material applied to the coat side and apply directly thereto the grit and binder hereinafter described.

The oil or bther presize, and the oil-or other backsize, may be cured at a temperature of about 130 F. for a period of about from 4 /2 to 24 hours, depending upon the nature of the material used and the amount of drier used therein. Where heavy blown China-wood oil is used, I prefer to use no drier, but the varnish made from Chinawood oil and containing a small amount of oil soluble Bakelite resin should preferably have added thereto about 0.3 to 1% of a manganese or cobalt drier.

After the coat sizing and backsizing applications have been cured, the paper is taken from the paper drying racks in the customary way and coated on the customary waterproof sandpaper machinery in the usual way. As the next step in the operation I apply to the .coat side of the paper, a binder such as that described in U. S. Patent No. 1,565,028 issued to Francis G. Okie dated December.8, 1925, and U. S. Reissue -Patent No. 17,584 reissued to Francis G. Okie on February 4, 1930, or I may use more recently developed binders such as the oil modified glyptals or varnishes prepared by the dissolving of oil soluble phenolic resins in China-wood oil during' The viscosity of the binder used will vary with the grit size. It is usually advantageous to start with a very viscous binder. A suitable viscosity for many purposes is a binder which tests body 0 when thinned to with Varnolene or high flash naphtha, the viscosity being measured at. a temperature of 77 F. with the Gardner-Holdt viscometer. The base binder is thinned according to the grit size it is intended to coat. By way of illustration, grit size 320 silicon carbide may be considered. For coating this grit, it will be found satisfactory to thin the base binder to 84% of as received and apply the binder to the paper at a temperature of 160 F. A suitable quantity of coat to apply is applied which may be the same or different material from that used as the first binder coat. In this case, however, it will be found advantageous to thin the binder to 65%. Suitable thinners as in the-former case are Varnolene or high flash naphtha, the thinner used depending upon the exact binder selected. A suitable temperature for application of the sand sizing coat is F. The sand sized coat is then dried for about 24 ours at a temperature; of about F.

If desired, by the use of a double sizer, a second backsize may be applied just before the sand size is applied, but in this case a very thin coat must be added to the paper to prevent sticking to the idler rolls used to carry the web to slats in the drying festoons which are customarily used in the manufacture of this type of sandpaper. After the sizing coat or sizing coats have been cured, the material may be taken from the racks in the form of a roll and'cut into the desired final forms for use, such for example as 9x 11" sheets.

It will thus be seen'that there has been provided by this invention an article and a method in which the various objects hereinabove set forth together with many thoroughly practical advantages are successfully achieved. As various possible embodiments mightbe made of the mechanical features of the..above invention and as the art herein described might be varied in various parts, all without departing from the scope of the invention, it is to be understood that all matter herenbefore set forth is to be interpreted as illustrati a'nd not in a limiting sense.

Iclaim:

l. Waterproof sandpaper, including a paper backing containing regenerated cellulose as an agent to impart wet strength, aWater-resistant paper treatment, a binder for abrasive grains and abrasive grains held to said backing by said binder.

2. Sandpaper, including a paper sheet containing regenerated cellulose as an agent to impart wet strength to the sheet, a binder for abrasive grains comprising synthetic resin, and abrasive grains held to said sheet by said binder.

3. Waterproof sandpaper, including a paper sheet controlling regenerated cellulose to impart wet strength to said sheet, said regenerated cellulose being derived from a water-dispersible colloid insolubilized in situ but in its insolubilized form being readily wetted by water and softened by water, whereby the sheet softened by water has a substantially higher wet strength than a sheet not containing said regenerated cellulose, a water-resistant sizing selected from the group consisting of the drying oils and varnishes superimposed upon the sheet and the regenerated cellulose, a binder coating comprising synthetic resin applied to at least one side of said sheet,

said binder coating being substantially a dis- 4. Waterproof sandpaper, including a paper sheet containing regeneratedcelluiose to impart wet strength to said sheet, said regenerated cellulose being derived from a water-dispersible colloid insoiubilized in situ but in its insoiubilized form being readily wetted by water and softened by water, whereby the sheet softened by water has a substantially higher wet strength than a sheet not containing said regenerated cellulose,

a water-resistant sizing selected from the group consisting of the drying oils and varnishes superimposed upon the sheet containing'the regenerated cellulose and said sizing being applied to the back side of the sheet, a binder coating com-, prising synthetic resin applied to the coat side of the sheet, said binder coating being substantially a discrete layer, and abrasive grains held to said sheet by said binder.

5. Waterproof sandpaper, including a paper sheet adapted to resist oil penetration, and containing regenerated cellulose to impart wet strength to said sheet, said regenerated cellulose being derived from a water-dispersible colloid insolubilized in situ but in its insoiubilized form being readily wetted by water and softened by water, whereby the sheet softened by water has a substantially higher wet strength than a sheet not containing said regenerated cellulose, a water-resistant sizing superimposed upon the sheet and the regenerated cellulose, a waterproof binder coating comprising synthetic resin applied to at least one side of the sheet, said binder coating being substantially a discrete layer, and abrasive grains held to said sheet by said binder.

6. Waterproof sandpaper, including a paper sheet containing regenerated cellulose to impart wet strength to said sheet, said regenerated cellulose being derived from a water-dispersible colloid insoiubilized in situ but in its insoiubilized form being readily wetted by water and softened by water, whereby the sheet softened by water has a substantially higher wet strength than a sheet not containing said regenerated cellulose, a binder coating comprising synthetic resin applied to the coat side of the sheet, said binder coating being substantially a discrete layer, and

abrasive grains held to said sheet by said binder.

7. Waterproof sandpaper, including a paper sheet containing regenerated cellulose to impart wet strength to said sheet, said regenerated cel- EVERETT G. HAM. 

